1. Field of the Invention
The present invention relates to a display device equipped with a display unit for displaying information such as characters and images.
2. Related Background Art
As a display device displaying information such as images by utilizing an electron beam, a device of a construction which uses a CRT (Cathode-ray Tube) as the display unit has been widely used. To generate an electron beam, a CRT of this type adopts a structure capable of supplying a high voltage of several tens of kV. Voltage is supplied to the cathode-ray tube by using an anode cap so that electrical discharge or the like may not occur. As shown in, for example, Japanese Patent Application Laid-Open No. 8-287851, a round insulating cap is used.
It is desired that the display unit is thin. Further, it is desired that not only its front surface but also its back surface is substantially flat, with the front and back surfaces being substantially parallel to each other. Recently, a thin, flat display device using liquid crystal has come into widespread use in place of the CRT. However, a display device using liquid crystal has a problem in that it has to be equipped with a back light since liquid crystal is not of a so-called self-luminous nature. Thus, there has been a demand for development of a self-luminous type display device.
As self-luminous type display devices, plasma displays have recently been commercialized. They are all thin and of large-screen type, commercially showing great promise. Further, parallel to the plasma displays, there exists a promising technique according to which a plurality of electron-emitting devices are arranged and applied to a flat display device, thereby obtaining a light emission of the same quality as that of the CRT. A number of proposals have been made regarding this technique. For example, Japanese Patent Application Laid-Open No. 4-163833 discloses a flat electron beam display device in which a vacuum panel contains a linear hot cathode and a complicated electrode structure. Known examples of the electron-emitting devices include a field emission device using an emitter cone, and a surface conduction electron-emitting device. Display devices using such electron devices are being studied.
Generally known examples of the construction of such a vacuum panel include one in which an electron source formed by arranging a plurality of electron-emitting devices in a matrix, a rear plate of glass on which drive wiring for driving the electron source is formed in a matrix, and a face plate of glass on which an accelerating electrode and phosphor are formed, are hermetically sealed by a seal bonding material through the intermediation of frames, and one in which hermetic sealing is effected solely by a seal bonding material when the gap between the face plate and the rear plate is small. In such a display device, display is effected by supplying various signal potentials to the display unit.
For example, in a CRT, there are supplied a potential for generating voltage for effecting electron emission from the electron-emitting device (electron gun), an anode potential, etc. In a plasma display panel, there is supplied a potential for generating voltage for generating plasma. In a flat panel display, in which electrons are emitted from electron-emitting devices arranged in a matrix to display an image or the like, there are supplied a potential for driving the matrix, a potential for accelerating electrons, etc.
Here, in a display device, by covering the terminal for supplying potential to the display unit with an insulator, it is possible to restrain the bad effect of the terminal potential on the other portions in the display device.
In a CRT, for example, an arrangement is known in which an anode potential of not less than 10 kV is used. In a display unit of the type in which a plurality of electron-emitting devices are dispersed in a plane and in which each electron-emitting device is independently driven, it is preferable to use an acceleration potential of not less than 700 V in the case of a so-called low-voltage drive type display unit and an acceleration potential of not less than 1 kV, more preferably, not less than 5 kV in the case of a high-voltage drive type display unit.
When using such a high potential, an arrangement is preferably adopted in which the potential supply terminal is covered with an insulator as in the case of a CRT, which uses an anode cap.
In order to realize a preferable insulator retaining construction for the case in which the terminal is covered with an insulator, the present inventor has conducted a study so as to develop a construction in which the insulator is directly attached to the display unit, with the insulator being retained solely by the attachment.
However, in this construction, it is necessary to firmly secure the display unit in position in order to reliably retain the insulator. Further, it is necessary to ensure a sufficient strength for the insulator. As the strength of the insulator increases, the size of the insulator also increases, so that it is rather difficult to achieve a reduction in the size of the entire display device (problem 1).
Further, in order to supply high potential to the terminal, a power source and a conductor cable for electrically connecting the power source and the terminal are used. In this case, in securing the conductor cable in position, fixing the conductor cable only at a predetermined position results in movement of the conductor cable caused on one side of that fixing point causing a movement in the reverse direction on the other side. Then, if a force is applied to the conductor cable as a result of vibration, shock, and interference with other components during transportation, a force is also applied to the terminal, so that there is the danger of the terminal being damaged (problem 2).
In a display device, there is provided not only a display unit but also drive circuits for driving the display unit. The drive circuits include a circuit for generating a signal to be supplied to the display unit, and a circuit for converting a signal input from the exterior of the display device into a signal suited to be supplied to the display unit. A signal for driving the display device is input and/or output to and/or from each of these circuits.
From the viewpoint of safety, reliability, and restraining of electromagnetic interference, these drive circuits must be protected from high voltage (problem 3).